1. Field of the invention
The present invention relates generally to automotive safety systems and more particularly to a capacitive occupancy detection apparatus for sensing the presence of a driver or passenger in a particular seat of an automobile and developing electronic logic when can be used in an automotive safety system.
2. Discussion of the Prior Art
For the past several years substantial legislative activity has concerned itself with requiring not only installation but enforced use of safety equipment in private automobiles. The first legislation enacted dealt simply with the required provision of safety equipment such as seat belts. This legislation was followed by subsequent laws requiring the provision of alarm devices to encourage use of the seat belts and subsequent standards now require that certain interlocking systems be provided in new model automobiles which prohibit operation of the automobile if the seat belt is not used. In order to assure that the seat belts are in fact used, the latest standards even require that a certain sequence of events occur before the engine may be started. This latter requirement serves a dual purpose of preventing operation of the vehicle unless the seat-belts are used, while at the same time making it more difficult for one temporarily incapacitated due to a state of inebriation, or the like, to operate the vehicle.
One of the problems encountered in implementing such requirements has been the lack of availability of suitable detecting apparatus capable of accurately detecting the presence of an occupant in a particular vehicle seat. Early detection apparatus utilized one or more mechanical switches which were actuated by body weight upon the seat. However, that type of detector has been found to be generally inadequate since its operation depends upon such variables as the structural characteristics of the seat materials, the temperature characteristics of the seat materials, the location of the switch relative to the seat structure itself, and the position and weight of a seat occupant.